The use of various types of devices for cleaning body tissue are known in the art. Some devices remove debris by suction while other devices remove debris by blowing debris away from the body tissue. An example of a surgical device that removes debris from a body tissue through suction is shown in U.S. Pat. No. 5,827,218. Other devices for cleaning body tissue include a combination of methods. An example of a device that employs multiple methods is shown in U.S. Pat. No. 5,902,264, which discloses an endoscopic surgical instruments for aspirating, irrigation and blowing gas adjacent to body tissue. These type of devices are well suited to cases where the body tissue is not adversely impacted by the cleaning action of the device. However, in some cases the body tissue is fragile and could be injured by a harsh cleaning action. In addition in some cases the body dynamics need to be considered, for example during the performance of an anastomosis, a more gentle or delicate removal of the debris proximate to a dynamic surgical site is necessary in order to preserve the integrity of the body tissue at the surgical site as blood exudes or flows from the anastomosis site.
One of such devices that have been developed for cleaning a surgical site during the performance of an anastomosis is a blower/mister, which relies on the atomization of liquid droplets. The blower/mister devices deliver a stream of pressurized gas that is intermixed with a stream of a sterile liquid to produce an intermixed stream of gas and liquid droplets, which can be used to wash debris away from the surgical site. In the blower/mister device a gas stream is directed past a liquid stream to entrain particles or droplets of the liquid in the gas stream, which results in an intermixed fluid stream of both gas and liquid droplets.
An example of a fluid entrainment device or atomization device is shown in U.S. Pat. No. 6,168,577. The fluid entrainment device contains coaxial lumens with liquid saline directed through a central lumen and a gas directed through an outer annular lumen. The gas flowing past the central stream of liquid saline entrains droplets of the saline with the gas stream. The intermixed liquid and gas stream is then directed at a surgical site to blow away debris from the surgical site.
U.S. Pat. No. 5,336,170 shows an example of another blower/mister having a fan shaped wand for blowing an intermixed gas and liquid stream onto a surgical site to blow debris away from the surgical site. One of the touted advantages of the blower/misters is that they have the ability to blow away debris from a surgical site without desiccating the tissue at the surgical site since they simultaneously deliver both a liquid and a gas to the surgical site.
Another type of blower mister, which moisturizes the fluid stream through entrainment or atomization of liquid droplets is shown in U.S. Pat. No. 6,156,003. The patent contends that the use of multiple smaller lumens each containing a liquid stream within a larger lumen containing a gas stream provides for greater efficiency in the atomization or entrainment of the liquid since the patent states smaller drops can be injected into the gas stream, which prevents liquid from dripping from his wand.
One of the more challenging tasks for a surgeon is forming an anastomosis on coronary arteries while the heart continues to beat. As the blood is pumped through the arteries it can disrupt the surgeons view of the surgical site, which further complicates the task of suturing the arteries under dynamic conditions. The suturing of an anastomosis is not only a dynamic task but also a delicate and difficult task since the ends of the arteries need to be viewed clearly in order to suture the ends of the arteries to each other. It is important that the surgeon not only have a clear view of the surgical site but he or she should have an assurance that the process of cleaning the surgical site does not harm the body tissue at the surgical site. Because of the difficult task in cleaning a dynamic surgical site without harming the tissue a tissue clearing device such as the blower/misters, which mix a gas stream and a liquid stream have been preferred. The blower/misters intermix a liquid stream and gas stream to produce a fluid stream, which is directed at the surgical site. The intermixing of the moving fluid streams occurs through a process of fluid entrainment whereby a gas stream and a liquid stream are directed along side each other. The friction between boundary layers of the two streams results in intermixing of the liquid droplets and the gas. Because of the need to enhance visualization at an anastomosis site where blood may be exuding or flowing from vessels the aforementioned devices for intermixing streams of both gas and liquid droplets, which are described in U.S. Pat. Nos. 6,168,577 and 5,336,170 have been used to blow away debris from delicate and dynamic surgical sites.
Although the aforedescribed blower/misters have been widely used to blow debris away from delicate and dynamic surgical sites they have the disadvantage that they may also introduce additional debris to the surgical site since the liquid droplets in the intermixed stream may remain at the surgical site, which has the potential to interfere with the surgeons view of the surgical site as well as affect the condition of the tissue at the surgical site. In addition, the liquid droplets, which have been entrained by the gas stream of the blower/misters, create multiple micro impacts on the tissue at the surgical site as one blows the intermixed gas and liquid stream at the surgical site. Consequently, the micro impacts of the liquid droplets have the potential to result in tissue damage at the surgical site. That is, even though the velocity of the gas stream and the velocity of the atomized liquid droplets may be the same the larger mass or momentum of the liquid droplets can generate a greater impact on the delicate tissue than the impingement of the molecules of the gas stream. Thus, while it may appear the velocity of the gas is sufficiently low so as not to harm the tissue the velocity of the liquid droplets may not be.
Another drawback with blower/misters is that oftentimes it is difficult to control the entrainment process as it often results in too much liquid saline solution or too little liquid saline solution being delivered to the surgical site.
A further disadvantage with the blower/misters is that the intermixed stream of liquid and gas leaves a residue of droplets of liquid debris at the surgical site. In addition, the liquid droplets may accumulate and coalesce at the end of the wand since the liquid droplets are always present when a two-phase stream is used to blow debris away from the surgical site.
While the use of blower/misters that intermix streams of liquid and gas are known in the art sometimes those who use the blower/misters mistakenly believe that devices that intermix the streams of liquid and gas humidify the gas, however, the coaction of fast moving streams of gas and liquid with each other actually produces entrainment or atomization of the liquid particles in the gas as opposed to humidification of the gas.
The invention described herein eliminates the problems of introducing extraneous foreign materials to the surgical site or the need for atomization of a liquid while at the same time inhibiting and preventing desiccation or injury to the tissue during the cleaning of a surgical site. The invention is well suited for cleaning and preserving tissue at delicate and dynamic surgical sites for example, an anastomosis site where blood may be exuding from a vessel during the surgical procedure. In addition the invention can eliminate the need for use of multiple fluid streams in cleaning a surgical site.